This invention generally relates to an antifouling system and, more particularly, to a modular arrangement of rubber tiles provided with a repetitive pattern of cells filled with compatible antifoulant materials which diffuse through the matrix of the rubber tile material.
Effective antifouling coatings include a means for transporting the antifouling materials to the boundary layer of the coating where fouling occurs. Mechanisms for transporting and releasing antifoulant include contact leaching and hydrolysis of the antifoulant; leaching of the antifoulant from a soluble matrix; and diffusion of antifoulant through the matrix. One problem encountered in utilizing the aforementioned release mechanisms is the difficulty of controlling the release rate of antifoulant from the coating. For example, too high of an antifoulant release rate has led to rapid exhaustion of antifoulant, and too low of a release rate often fails to adequately protect the coating surface from fouling. After a period of time, antifouling materials in coating matrixes become so diluted that the coatings lose antifouling effectiveness the coating must be replaced. The antifouling coating system of the present invention overcomes problems of the prior art by utilizing reservoirs that permit insitu replenishment of antifoulant.
In a diffusion type of coating, the antifoulant diffuses throughout the coating matrix. As the antifoulant material passes into the seawater from the boundary layer of the coating, the remaining antifouling material redistributes itself in an attempt to maintain equilibrium within the coating. If the diffusion or migration rate is suitably controlled it is possible to maintain an antifouling environment in which the release rate of antifoulant from the boundary layer of the coating is slightly greater than the threshold tolerance levels of the fouling organisms. One type of diffusion system utilized to control the rate of release and thereby provide a long service life involves the use two coating layers where the outer coating serves as a diffusion layer and the inner layer served as a reservoir for the surplus antifoulant. However, multi-coat systems are difficult to manufacture and properly apply to the ship hull, and the release rate is greatly affected by the thickness of the outer diffusion layer.